Device and method to seal boreholes

ABSTRACT

Apparatus and methods are described that are particularly suited for creating a seal in a borehole annulus. In one embodiment, an outer surface  10   s  of an expandable conduit  10  is provided with a formation  20  that includes an elastomeric material (e.g. a rubber) that can expand and/or swell when the material comes into contact with an actuating agent (e.g. water, brine, drilling fluid etc). The expandable conduit  10  is located inside a second conduit (e.g. a pre-installed casing, liner or open borehole) and radially expanded. The actuating agent can be naturally occurring in the borehole or can be injected or pumped therein to expand or swell the elastomeric material to create the seal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of PCT International application numberPCT/GB02/00362 filed on Jan. 28, 2002, entitled “Device and Method toSeal Boreholes”, which claims benefit of British application serialnumber 0102023.9, filed on Jan. 26, 2001 and British application serialnumber 0102526.1, filed on Feb. 1, 2001.

The present invention relates to apparatus and methods for sealing anannulus in a borehole. The present invention can also be used to sealand lock expandable tubular members within cased, lined, and inparticular, open-hole boreholes.

DESCRIPTION OF THE RELATED ART

It is known to use expandable tubular members, e.g. liners, casing andthe like, that are located in a borehole and radially expanded in situby applying a radial expansion force using a mechanical expander deviceor an inflatable element, such as a packer. Once the expandable memberhas been expanded into place, the member may not contact the conduit(e.g. liner, casing, formation) in which it is located along the entirelength of the member, and a seal is generally required against theliner, casing or formation to prevent fluid flow in an annulus createdbetween the expandable member and the liner, casing or formation, andalso to hold differential pressure. The seal also helps to preventmovement of the expandable member that may be caused by, for example,expansion or contraction of the member or other tubular members withinthe borehole, and/or accidental impacts or shocks.

When running and expanding in open-hole applications or within damagedor washed-out casing, liner etc, the diameter of the borehole or thecasing, liner etc may not be precisely known as it may vary over thelength of the borehole because of variations in the different materialsin the formation, or variations in the internal diameter of the downholetubulars. In certain downhole formations such as washed-out sandstone,the size of the drilled borehole can vary to a large extent along thelength or depth thereof.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda seal for use in a borehole, the seal comprising an elastomericmaterial that is capable of expanding upon contact with an actuatingagent.

According to a second aspect of the present invention, there is provideda method of creating a seal in a borehole, the method comprising thesteps of providing an elastomeric material in the borehole and exposingthe material to an actuating agent that causes the elastomeric materialto expand.

The seal is preferably expanded in an annulus to seal the annulus or aportion thereof.

The elastomeric material is typically a rubber. The elastomeric materialcan be NITRILE™, VITON™, AFLAS™, Ethylene-propylene rubbers (EPM orEPDM) or KALREZ™, although other suitable materials may also be used.Any elastomeric material may be used. The choice of elastomeric materialwill largely depend upon the particular application and the actuatingagent. Also, the fluids that are present downhole will also determinewhich elastomeric material or actuating agent can be used.

The actuating agent typically comprises a water- or mineral-based oil orwater. Production and/or drilling fluids (e.g. brine, drilling mud orthe like) may also be used. Hydraulic oil may be used as the actuatingagent. Any fluid that reacts with a particular elastomeric material maybe used as the actuating agent. The choice of actuating agent willdepend upon the particular application, the elastomeric material and thefluids that are present downhole.

The actuating agent may be naturally occurring downhole, or can beinjected or pumped into the borehole. Alternatively, a container (e.g. abag) of the actuating agent can be located at or near the elastomericmaterial where the container bursts upon radial expansion of theconduit. Thus, the actuating agent comes into contact with theelastomeric material causing it to expand and/or swell.

The elastomeric material is typically applied to an outer surface of aconduit. The conduit can be any downhole tubular, such as drill pipe,liner, casing or the like. The conduit is preferably capable of beingradially expanded, and is thus typically of a ductile material.

The conduit can be a discrete length or can be in the form of a stringwhere two or more conduits are coupled together (e.g. by welding, screwthreads etc). The elastomeric material can be applied at two or moreaxially spaced-apart locations on the conduit. The elastomeric materialis typically applied at a plurality of axially spaced-apart locations onthe conduit.

The conduit is typically radially expanded. The conduit is typicallylocated in a second conduit before being radially expanded. The secondconduit can be a borehole, casing, liner or other downhole tubular.

The elastomeric material can be at least partially covered or encased ina non-swelling and/or non-expanding elastomeric material. Thenon-swelling and/or non-expanding elastomeric material can be anelastomer that swells in a particular fluid that is not added orinjected into the borehole, or is not naturally occurring in theborehole. Alternatively, the non-swelling and/or non-expandingelastomeric material can be an elastomer that swells to a lesser extentin the naturally occurring, added or injected fluid.

As a further alternative, a non-swelling polymer (e.g. a plastic) may beused in place of the non-swelling and/or non-expanding elastomericmaterial. The non-swelling polymer can be TEFLON™, RYTON™ or PEEK™.

The elastomeric material may be in the form of a formation. Theformation can comprise one or more bands of the elastomeric material,the bands typically being annular. Alternatively, the formation maycomprise two outer bands of a non-swelling and/or non-expandingelastomeric material (or other rubber or plastic) with a band ofswelling elastomeric material therebetween. A further alternativeformation comprises one or more bands of elastomeric material that aremore or less covered or encased in a non-swelling and/or non-expandingelastomeric (or other) material. At least a portion of the elastomericmaterial is typically not covered by the non-swelling and/ornon-expanding material. The uncovered portion of the elastomericmaterial typically facilitates contact between the material and theactuating agent. Other formations may also be used.

The elastomeric material typically swells upon contact with theactuating fluid due to absorption of the fluid by the material.Alternatively, or additionally, the elastomeric material can expandthrough chemical attack resulting in a breakdown of cross-linked bonds.

The elastomeric material typically expands and/or swells by around 5% to200%, although values outwith this range are also possible. Theexpansion and/or swelling of the elastomeric material can typically becontrolled. For example, restricting the amount of actuating agent cancontrol the amount of expansion and/or swelling. Also, reducing theamount of elastomeric material that is exposed to the actuating agent(e.g. by covering or encasing more or less of the material in anon-swelling material) can control the amount of expansion and/orswelling. Other factors such as temperature and pressure can also affectthe amount of expansion and/or swelling, as can the surface area of theelastomeric material that is exposed to the actuating agent.

Optionally, the expansion and/or swelling of the elastomeric materialcan be delayed for a period of time. This allows the conduit to belocated in the second conduit and radially expanded before theelastomeric material expands and/or swells. Chemical additives can becombined with the base formulation of the swelling elastomeric materialto delay the swelling for a period of time. The period of time can beanything from a few hours to a few days. The particular chemicaladditive that is used typically depends upon the structure of the basepolymer in the elastomeric material. Pigments such as carbon black,glue, magnesium carbonate, zinc oxide, litharge and sulphur are known tohave a slowing or delaying influence on the rate of swelling.

As an alternative to this, a water- or other alkali-soluble material canbe used, where the soluble material is at least partially dissolved uponcontact with a fluid, or by the alkalinity of the water.

The method typically includes the additional step of applying theelastomeric material to an outer surface of a conduit. The conduit canbe any downhole tubular, such as drill pipe, liner, casing or the like.The conduit is preferably capable of being radially expanded, and isthus typically of a ductile material.

The method typically includes the additional step of locating theconduit within a second conduit. The second conduit may comprise aborehole, casing, liner or other downhole tubular.

The method typically includes the additional step of applying a radialexpansion force to the conduit. The radial expansion force typicallyincreases the inner and outer diameters of the conduit. The radialexpansion force can be applied using an inflatable element (e.g. apacker) or an expander device (e.g. a cone). The conduit can be restedon top of the inflatable element or the expander device as it is runinto the second conduit.

The method typically includes the additional steps of providing anexpander device and pushing or pulling the expander device through theconduit. The expander device is typically attached to a drill string,coiled tubing string, wireline or the like, but can be pushed or pulledthrough the second conduit using any conventional means.

Alternatively, the method typically includes the additional steps ofproviding an inflatable element and actuating the inflatable element.The inflatable element can be attached to a drill string, coiled tubingstring or wireline (with a downhole pump). Optionally, the method mayinclude one, some or all of the additional steps of deflating theinflatable element, moving it to another location, and re-inflating itto expand a further portion of the conduit.

The method optionally includes the additional step of injecting orpumping the actuating agent into the borehole.

The method optionally includes the additional step of temporarilyanchoring the conduit in place. This provides an anchor point for theradial expansion of the conduit. A packer, slips or the like can be usedfor this purpose. The inflatable element is optionally used to expand aportion of the conduit against the second conduit to act as an anchorpoint.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the present invention shall now be described, by way ofexample only, with reference to the accompanying drawings, in which:—

FIG. 1 is a first embodiment of a formation applied to an outer surfaceof a conduit;

FIG. 2 is a second embodiment of a formation applied to an outer surfaceof a conduit;

FIG. 3 a is a third embodiment of a formation applied to an outersurface of a conduit; and

FIG. 3 b is a cross-sectional view through a portion of the conduit ofFIG. 3 a.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIG. 1 shows a conduit 10 that is providedwith a first embodiment of a formation 20 on an outer surface 10 sthereof. The formation 20 includes a plurality of bands 22 that arerounded on their outer edges 22 o and are joined by a plurality ofvalleys 24 therebetween. The bands 22 and valleys 24 provide an overallribbed profile to the formation 20.

Formation 20 is typically comprised of an elastomeric material that canexpand and/or swell due to contact with an actuating agent such as afluid. The expansion and/or swelling of the elastomeric material resultsin increased dimensional properties of the elastomeric material in theformation 20. That is, the material forming the bands 22 and valleys 24will expand or swell in both the longitudinal and radial directions, theamount of expansion- or swelling depending on the amount of actuatingagent, the amount of absorption thereof by the elastomeric material andthe amount of the elastomeric material itself. It will also beappreciated that for a given elastomeric material, the amount ofswelling and/or expansion is a function not only of the type ofactuating agent, but also of physical factors such as pressure,temperature and the surface area of material that is exposed to theactuating agent.

The expansion and/or swelling of the elastomeric material can take placeeither by absorption of the actuating agent into the porous structure ofthe elastomeric material, or through chemical attack resulting in abreakdown of cross-linked bonds. In the interest of brevity, use of theterms “swell” and “swelling” or the like will be understood also torelate to the possibility that the elastomeric material mayadditionally, or alternatively expand.

The elastomeric material is typically a rubber material, such asNITRILE™, VITON™, AFLAS™, Ethylene-propylene rubbers (EPM or EPDM) andKALREZ™. The actuating agent is typically a fluid, such as hydraulic oilor water, and is generally an oil- or water-based fluid. For example,brine or other production or drilling fluids (e.g. mud) can be used tocause the elastomeric material to swell. The actuating agent used toactuate the swelling of the elastomeric material can either be naturallyoccurring in the borehole itself, or specific fluids or chemicals thatare pumped or injected into the borehole.

The type of actuating agent that causes the elastomeric material toswell generally depends upon the properties of the material, and inparticular the hardening matter, material or chemicals used in theelastomeric material.

Table 1 below gives examples of fluid swell for a variety of elastomericmaterials, and the extent to which they swell when exposed to certainactuating agents.

TABLE 1 Swelling Media (at 300° F.) Expansion with Expansion WithMaterial Hydraulic Oil Water NITRILE ™  15% 10% VITON ™  10% 20% AFLAS ™ 30% 12% EPDM 200% 15% KALREZ ™  5% 10%

As indicated above, the amount of swelling of the elastomeric materialdepends on the type of actuating agent used to actuate the swelling, theamount of actuating agent and the amount and type of elastomericmaterial that is exposed to the actuating agent. The amount of swellingof the elastomeric material can be controlled by controlling the amountof fluid that is allowed to contact the material and for how long. Forexample, the material may only be exposed to a restricted amount offluid where the material can only absorb this restricted amount. Thus,swelling of the elastomeric material will stop once all the fluid hasbeen absorbed by the material.

The elastomeric material can typically swell by around 5% (or less) toaround 200% (or more), depending upon the type of elastomeric materialand actuating agent used. If the particular properties of the materialand the amount of fluid that the material is exposed to are known, thenit is possible to predict the amount of expansion or swelling. It isalso possible to predict how much material and fluid will be required tofill a known volume.

The structure of the formation 20 can be a combination of swelling orexpanding and non-swelling or non-expanding elastomers, and the outersurfaces of the formation 20 may be profiled to enable maximum materialexposure to the swelling or expanding medium. In the interest ofbrevity, non-swelling and non-expanding elastomeric material will bereferred to commonly by “non-swelling”, but it will be appreciated thatthis may include non-expanding elastomeric materials also.

The formation 20 is typically applied to the outer surface 10 s of theconduit 10 before it is radially expanded. Conduit 10 can be anydownhole conduit that is capable of sustaining plastic and/or elasticdeformation, and can be a single length of, for example, liner, casingetc. However, conduit 10 may be formed of a plurality of lengths ofcasing, liner or the like that are coupled together using anyconventional means, e.g. screw threads, welding etc.

Formation 20 is typically applied at axially spaced-apart locationsalong the length of conduit 10, although it may be provided continuouslyover the length of the conduit 10 or a portion thereof. It will beappreciated that the elastomeric material will require space into whichit can swell, and thus it is preferable to have at least some spacingbetween the formations 20. The elastomeric material of the or eachformation 20 is typically in a solid or relatively solid form so that itcan be attached or bonded to the outer surface 10 s and remain there asthe conduit 10 is run into the borehole, casing, liner or the like.

Once the borehole has been drilled, or in the case of a borehole that isprovided with pre-installed casing, liner or the like, conduit 10 islocated in the borehole, casing, liner or the like and radially expandedusing any conventional means. This can be done by using an inflatableelement (e.g. a packer) or an expander device (e.g. a cone) to apply aradial expansion force. The conduit 10 typically undergoes plasticand/or elastic deformation to increases its inner and outer diameters.

The expansion of conduit 10 is typically not sufficient to expand theouter surface 10 s into direct contact with the formation of theborehole or pre-installed casing, liner or the like, although this maynot always be the case. For example, certain portions of the conduit 10may contact the formation at locations along its length due to normalvariations in the diameter of the borehole during drilling, and/orvariations in the diameter of the conduit 10 itself. Thus, an annulus istypically created between the outer surface 10 s and the borehole,casing, liner etc.

It will be appreciated that the elastomeric material in the or eachformation 20 may begin to swell as soon as the conduit 10 is located inthe borehole as the fluid that actuates the swelling may be naturallyoccurring in the borehole. In this case, there is generally norequirement to inject chemicals or other fluids to actuate the swellingof the elastomeric material.

However, the elastomeric material may only swell when it comes intocontact with particular fluids that are not naturally occurring in theborehole and thus the fluid will require to be injected or pumped intothe annulus between the conduit 10 and the borehole, casing, liner orthe like. This can be done using any conventional means.

As an alternative to this, a bag or other such container 11 thatcontains the actuating fluid can be attached to the outer surface 10 sat or near to the or each formation 20. Indeed, the bag or the like canbe located over the or each formation 20. Thus, as the conduit 10 isradially expanded, the bag ruptures causing the actuating fluid tocontact the elastomeric material.

It will be appreciated that it is possible to delay the swelling of theelastomeric material. This can be done by using chemical additives inthe base formulation that causes a delay in swelling. The type ofadditives that may be added will typically vary and may be different foreach elastomeric material, depending on the base polymer used in thematerial. Typical pigments that can be added that are known to delay orhaving a slowing influence on the rate of swelling include carbon black,glue, magnesium carbonate, zinc oxide, litharge and sulphur.

As an alternative, the elastomeric material can be at least partially ortotally encased in a water-soluble or alkali-soluble polymeric covering.The covering can be at least partially dissolved by the water or thealkalinity of the water so that the actuating agent can contact theelastomeric material thereunder. This can be used to delay the swellingby selecting a specific soluble covering that can only be dissolved bychemicals or fluids that are injected into the borehole at apredetermined time.

The delay in swelling can allow the conduit 10 to be located in theborehole, casing, liner or the like and expanded into place before theswelling or a substantial part thereof takes place. The delay inswelling can be any length from hours to days.

As the elastomeric material swells, it expands and thus creates a sealin the annulus. The seal is independent of the diameter of the borehole,casing, liner or the like as the material will swell and continue toswell upon absorption of the fluid to substantially fill the annulusbetween the conduit 10 and the borehole, casing, liner or the like inthe proximity of the formation 20. As the elastomeric material swellsand continues to do so, it will come into contact with the formation ofthe borehole, casing, liner or the like and will go into a compressivestate to provide a tight seal in the annulus. Not only does theelastomeric material act as a seal, but it will also tend to lock theconduit 10 in place within the borehole, casing, liner or the like.

Upon swelling, the elastomeric material retains sufficient mechanicalproperties (e.g. hardness, tensile strength, modulus of elasticity,elongation at break etc) to withstand differential pressure between theborehole and the inside of the liner, casing etc. The mechanicalproperties that are retained also ensure that the elastomeric materialremains bonded to the conduit 10. The mechanical properties can bemaintained over a significant time period so that the seal created bythe swelling of the elastomeric material does not deteriorate over time.

It will be appreciated that the mechanical properties of the elastomericmaterial can be adjusted or tuned to specific requirements. Chemicaladditives such as reinforcing agents, carbon black, plasticisers,accelerators, activators, anti-oxidants and pigments may be added to thebase polymer to have an effect on the final material properties,including the amount of swell. These chemical additives can vary orchange the tensile strength, modulus of elasticity, hardness and otherfactors of the elastomeric material.

The resilient nature of the elastomeric material can serve to absorbshocks and impacts downhole, and can also tolerate movement of theconduit 10 (and other downhole tubular members) due to expansion andcontraction etc.

Referring to FIG. 2, there is shown an alternative formation 30 that canbe applied to an outer surface 40 s of a conduit 40. Conduit 40 can bethe same or similar to conduit 10. As with formation 20, formation 30can be applied at a plurality of axially spaced-apart locations alongthe length of the conduit 40. Conduit 40 may be a discrete length ofdownhole tubular that is capable of being radially expanded, or cancomprise a length of discrete portions of downhole tubular that arecoupled together (e.g. by welding, screw threads etc).

The formation 30 comprises two outer bands 32, 34 of a non-swellingelastomeric material with an intermediate band 36 of a swellingelastomeric material therebetween. It will be appreciated that theintermediate band 36 has been provided with a ribbed or serrated outerprofile to provide a larger amount of material (i.e. an increasedsurface area) that is exposed to the actuating fluid that causesswelling. The use of the outer bands 32, 34 of a non-swellingelastomeric material can allow the amount of swelling of theintermediate band 36 of the elastomeric material to be controlled. Thisis because the two outer bands 32, 34 can limit or otherwise restrictthe amount of swelling of the elastomeric material (i.e. band 36) in theaxial directions. Thus, the swelling of the material will besubstantially constrained to the radial direction.

The non-swelling elastomeric material can be an elastomer that swells ina particular fluid that is not added or injected into the borehole, oris not naturally occurring in the borehole. Alternatively, thenon-swelling elastomeric material can be an elastomer that swells to alesser extent in the naturally occurring, added or injected fluid. Forexample, and with reference to Table 1 above, if hydraulic oil is beingused as the actuating fluid, then the elastomeric material could be EPDM(which expands by around 200% in hydraulic oil) and the non-swellingelastomeric material could be KALREZ™ as this only swells by around 5%in hydraulic oil.

As a further alternative, a non-swelling polymer (e.g. a plastic) may beused in place of the non-swelling elastomeric material. For example,TEFLON™, RYTON™ or PEEK™ may be used.

It will be appreciated that the term “non-swelling elastomeric material”is intended to encompass all of these options.

The outer bands 32, 34 of a non-swelling elastomeric material alsoprovides a mechanism by which the swelling of the elastomeric materialin intermediate band 36 can be controlled. For example, when the conduit10 is radially expanded, the bands 32, 34 of the non-swellingelastomeric material will also expand, thus creating a partial seal inthe annulus between the outer surface 10 s of the conduit 10 and theborehole, casing, liner or the like. The partial seal reduces the amountof fluid that can by-pass it and be absorbed by the swelling elastomericmaterial of band 36. This restriction in the flow of fluid can be usedto delay the swelling of the elastomeric material in band 36 byrestricting the amount of fluid that can be absorbed by the material,thus reducing the rate of swelling.

The thickness of the bands 32, 34 in the radial direction can be chosento allow either a large amount of fluid to seep into band 36 (i.e. bymaking the bands relatively thin) or a small amount of fluid (i.e. bymaking the bands relatively thick). If the bands 32, 34 are relativelythick, a small annulus will be created between the outer surface of thebands 32, 34 and the borehole etc, thus providing a restriction to thefluid. The restricted fluid flow will thus cause the elastomericmaterial to swell more slowly. However, if the bands 32, 34 arerelatively thin, then a larger annulus is created allowing more fluid toby-pass it, and thus providing more fluid that can swell the elastomericmaterial.

Additionally, the two outer bands 32, 34 can also help to preventextrusion of the swelling elastomer material in band 36. The swellingelastomeric material in band 36 typically gets softer when it swells andcan thus extrude. The non-swelling material in bands 32, 34 can help tocontrol and/or prevent the extrusion of the swelling elastomericmaterial. It will be appreciated that the bands 32, 34 reduce the amountof space into which the swelling material of band 36 can extrude andthus by reducing the space into which it can extrude, the amount ofextrusion can be controlled or substantially prevented. For example, ifthe thickness of the bands 32, 34 is such that there is very little orno space into which the swelling elastomeric material can extrude into,then this can stop the extrusion. Alternatively, the thickness of thebands 32, 34 can provide only a relatively small space into which theswelling elastomeric material can extrude into, thus substantiallycontrolling the amount of extrusion.

FIGS. 3 a and 3 b show a further formation 50 that can be applied to anouter surface Gos of a conduit 60. Conduit 60 can be the same as orsimilar to conduits 10, 40 and may be a discrete length of downholetubular that is capable of being radially expanded, or can comprise alength of discrete portions of downhole tubular that are coupledtogether (e.g. by welding, screw threads etc).

Formation 50 comprises a number of axially spaced-apart bands 52 thatare typically annular bands, but this is not essential. The bands 52 arelocated symmetrically about a perpendicular axis so that the sealscreated upon swelling of the elastomeric material within the bands holdpressure in both directions.

The bands 52 are typically lip-type seals. As can be seen from FIG. 3 bin particular, the bands 52 have an outer covering 52 o of anon-swelling elastomer, and an inner portion 52 i of a swellingelastomeric material. One end 52 a of the band 52 is open to fluidswithin the borehole, whereas the outer covering 52 o encases theremainder of the elastomeric material, thus substantially preventing theingress of fluids.

The swelling of the elastomeric material in inner portion 52 i isconstrained by the outer covering 52 o, thus forcing the material toexpand out end 52 a. This creates a seal that faces the direction ofpressure. With the embodiment shown in FIG. 3 a, four seals areprovided, with two facing in a first direction and two facing in asecond direction. The second direction is typically opposite the firstdirection. This provides a primary and a back-up seal in each direction,with the seal facing the pressure.

The outer covering 52 o can also help to prevent or control theextrusion of the elastomeric material in inner portion 52 i as describedabove.

Thus, certain embodiments of the present invention provide apparatus andmethods for creating seals in a borehole that use the swellingproperties of elastomeric materials to create the seals. Certainembodiments of the present invention can also prevent swelling of thematerial until the conduit to which it is applied has been radiallyexpanded in situ. Modifications and improvements may be made to theforegoing without departing from the scope of the present invention.

1. A seal for use in a borehole, the seal comprising an elastomericmaterial that is capable of expanding or swelling upon contact with anactuating agent, wherein the elastomeric material is applied to asurface of a radially expandable conduit, the expandable conduit havinga first diameter prior to expansion and a second larger diameter afterexpansion, wherein the seal is an annular seal configured to seal anannulus between the expandable conduit and the borehole.
 2. The sealaccording to claim 1, wherein the elastomeric material comprises arubber.
 3. The seal according to claim 1, wherein the elastomericmaterial is selected from the group consisting of NITRILE, VITON™,AFLAS™, Ethylene-propylene rubbers and KALREZ™.
 4. The seal according toclaim 1, wherein the actuating agent is selected from the groupconsisting of a water-based oil, a mineral-based oil and a mineral-basedwater.
 5. The seal according to claim 1, wherein the actuating agent isnaturally occurring downhole.
 6. The seal according to claim 1, whereinthe elastomeric material is applied to an outer surface of the conduit.7. The seal according to claim 6, wherein the elastomeric material isapplied to at least two axially spaced-apart locations on the conduit.8. The seal according to claim 6, wherein the conduit is radiallyexpanded.
 9. The seal according to claim 8, wherein the conduit islocated in a second conduit before being radially expanded.
 10. The sealaccording to claim 1, wherein the elastomeric material swells uponcontact with the actuating fluid due to absorption of the fluid by theelastomeric material.
 11. The seal according to claim 1, wherein theelastomeric material is expandable through chemical attack resulting ina breakdown of cross-linked bonds.
 12. A sealing apparatus for isolatinga tubular, comprising: a tubular body configured to be expandeddownhole; one or more swelling elastomers disposed around an outersurface of the tubular body; a tubular expander device; and a cover atleast partially disposed on a portion of the one or more swellingelastomers.
 13. The apparatus of claim 12, wherein the one or moreswelling elastomers are activated by a wellbore fluid.
 14. The apparatusof claim 12, wherein expanding the tubular body causes the cover tobecome more permeable to an activating agent.
 15. The apparatus of claim12, wherein the one or more swelling elastomers include at least onehydrocarbon activated swelling elastomer and at least one wateractivated swelling elastomer.
 16. The apparatus of claim 12, wherein thetubular body comprises an expandable tubular body.
 17. The apparatus ofclaim 12, wherein the cover substantially prevents the one or moreswelling elastomers from activating.
 18. An apparatus for isolating awell, comprising: a tubular having a first sealing member and a secondsealing member, wherein the tubular has a first diameter and a largersecond diameter due to radial expansion of the tubular, wherein each ofthe sealing members include: a tubular body; and one or more swellingelements disposed around an inner surface of the tubular body.
 19. Theapparatus of claim 18, further comprising a protective layer disposedaround the one or more swelling elements.
 20. The apparatus of claim 19,wherein the cover substantially prevents the one or more swellingelastomers from activating.
 21. The apparatus of claim 20, whereinexpanding the tubular body causes the cover to become more permeable toan activating agent.
 22. A method for isolating a well, comprising:running a sealing apparatus into the wellbore, the sealing apparatusincluding: a tubular body; and a swelling element disposed around anouter surface of the tubular body; expanding the tubular body; andcausing the swelling element to swell and contact the wellbore.
 23. Themethod of claim 22, wherein the sealing apparatus further comprises aprotective cover at least partially disposed on a portion of theswelling element.
 24. The method of claim 23, wherein expanding thetubular body causes the protective cover to become more permeable to anactivating agent.
 25. The method of claim 22, wherein the sealingapparatus further comprises a non-swelling element dispose adjacent tothe swelling element.
 26. The method of claim 22, wherein the tubularbody comprises an expandable tubular.
 27. The method of claim 22,further comprising exposing the swelling element to an activating agent.28. The method of claim 27, wherein the swelling element comprises anelastomer.
 29. The method of claim 28, wherein the swelling elementswells when exposed to an activating agent.
 30. A method of sealing awellbore, comprising: running a tubular into the wellbore to apredetermined location, the tubular having one or more elements capableof swelling when exposed to an activating fluid; exposing the one ormore elements to the activating fluid in the wellbore, thereby causingthe one or more elements disposed around an outer surface of the tubularto swell; expanding the tubular; and sealing the wellbore as a result ofthe swelling.
 31. The method of claim 30, wherein the one or moreelements swell at a delayed rate to allow the placement of the tubularat the predetermined location.
 32. The method of claim 30, wherein thetubular is expanded prior to allowing the one or more elements tocompletely swell radial outward.
 33. The method of claim 30, furtherincluding locating the tubular within a second tubular to effect a sealbetween the tubulars.
 34. A conduit assembly for use in a wellbore, theassembly comprising: a conduit having a first diameter before radialexpansion and a second increased diameter after radial expansion; asecond conduit; and an elastomeric material adapted to swell on contactwith an actuating agent, wherein the expandable conduit is arrangedwithin the second conduit and wherein the elastomeric material isprovided therebetween.
 35. A method of sealing two conduits, the methodcomprising: providing a circumferentially continuous walled radiallyexpandable conduit, a second conduit and a swellable elastomericmaterial, wherein the second conduit is a wellbore; locating thecircumferentially continuous walled expandable conduit within the secondconduit such that the swellable elastomeric material is located betweenthe circumferentially continuous walled radially expandable conduit andthe second conduit; applying a radial expansion force to thecircumferentially continuous walled expandable conduit; and exposing theelastomeric material to an actuating agent which causes the elastomericmaterial to swell within an annulus between the conduits.
 36. The methodof claim 35, wherein the wellbore is a wellbore casing.
 37. An annularseal for use in a wellbore comprising: a tubular configured to beradially expanded in the wellbore; an expansion device for radiallyexpanding the tubular; and an elastomeric material on an outer surfaceof the tubular, wherein the material that is configured to expand uponcontact with an actuating agent.
 38. The annular seal of claim 37further comprising the tubular having a first unexpanded diameter and asecond expanded diameter.
 39. A seal for use in a borehole, the sealcomprising: an elastomeric material that is capable of expanding orswelling upon contact with an actuating agent, wherein the elastomericmaterial is applied to a surface of a radially expandable conduit, theexpandable conduit having a first diameter prior to expansion and asecond larger diameter after expansion, wherein a container retainingthe actuating agent is located near the elastomeric material and whereinthe container releases the actuating agent upon radial expansion of theconduit.
 40. A seal for use in a borehole, the seal comprising: anelastomeric material that is capable of expanding or swelling uponcontact with an actuating agent, wherein the elastomeric material isapplied to a surface of a radially expandable conduit, the expandableconduit having a first diameter prior to expansion and a second largerdiameter after expansion, wherein the elastomeric material is at leastpartially covered in a material selected from the group consisting of anon-swelling elastomeric material, a non-expanding elastomeric material,and a non-swelling polymer.
 41. A seal for use in a borehole, the sealcomprising: an elastomeric material that is capable of expanding orswelling upon contact with an actuating agent, wherein the elastomericmaterial is applied to a surface of a radially expandable conduit, theexpandable conduit having a first diameter prior to expansion and asecond larger diameter after expansion, wherein the actuating agent is awater.
 42. A sealing apparatus for isolating a tubular, comprising: atubular body configured to be expanded downhole the tubular having afirst unexpanded diameter and a second larger expanded diameter; one ormore swelling elastomers disposed around an outer surface of the tubularbody; and a cover at least partially disposed on a portion of the one ormore swelling elastomers.